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[moved] 24,000j Capacitor Bank (Now Complete)

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teravolt

Thu Jan 31 2008, 03:36AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

nice bank does it have gradeing resistors for equal charging? Be careful it is a pausible explosion hazard

FastMHz

Thu Jan 31 2008, 05:57AM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

I have 3 fuses in my charger...one on the input, and on each MOT output before the diodes...this way, I can't possibly over-current my diodes, or overload the charger's built in variac I'm using to slowly ramp up the charge on the bank - the variac is my current limiting. In my experimentation so far I've found the strings charging to within a couple of volts of each other, they are really well matched; and of course I will keep monitoring this as I use the bank to ensure that an individual string never gets "out of line".

I was thinking...what about placing a clamping diode on each string? The diodes would prevent any individual string from being reverse charged... The problem then is where to find diodes big enough to handle this...x 10

Shaun

Thu Jan 31 2008, 06:37AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Oh yea, thats another good point...what kind of diodes will stand up to back EMF from a 24kJ bank? Well, whatever type of diode you pick, encase it in something because after the coil itself I think the flywheel diode is most likely to detonate.

I want to make a suggestion better than a bunch of big brick diodes in parallel, but its late (early?), and I can't think of any.

teravolt

Fri Feb 01 2008, 05:15AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

depending on age and condition I don't think it will be necisary if each bank is balanced and exersized.

teslacoolguy

Fri Feb 01 2008, 09:56PM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

i would be afraid that the cap bank will not stand up to such high reverse voltage but than again i might be wrong

ramses

Sat Feb 02 2008, 02:58AM

Registered Member #1208 Joined: Thu Jan 03 2008, 05:30PM
Location: Chesterland, OH
Posts: 154

if it couldn't take it, it would SUCK to loose 100 cap's just like that. i have no idea what i would do to myself if i did that. i have heard of aluminum strips in electrolyte being kind of a rectifier, conducting in one direction and not in the other. i don't know if 'lyics act the same way, but my 'lyics conduct when the polarity is wrong. as long as you don't use a SCR(good luck finding one) they should ring down unless your coil blows, but i wouldn't risk it without research, life insurance, and something to hide behind.

just stay away from inductive loads and you should be fine :( happy diode hunting!

FastMHz

Tue Feb 05 2008, 06:45PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

My small scaled triggered spark gap worked 100% reliably!!!!! I successfully remote control discharged a 5kv capacitor by turning on an ignition transformer with a remote button. It worked as low as 1.5kv up to 5kv. I figure on the full scale one the electrodes should be easily adjustable so that voltages as low as 500v can be used, hopefully. I don't want to be stuck only being able to discharge a fully loaded bank as that severely limits experimentation potential.

FastMHz

Thu Feb 07 2008, 07:31PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

I've finally got my full scale triggered gap complete!

Sparkgapdg9

The entire system has now been completed....my full size triggered spark gap works like a charm. I charged the 24kj bank to a low value of ~3.5kj and discharged into a coil a couple of times....except I have a problem...the 10kv transformer on the gap is backfeeding to my main charger and fried the diodes, which are 8kv. So I either need to disconnect the charger from the bank before discharging, or find diodes of higher voltage to put in the charger.

After sleeping on this problem, I've decided I'm going to disconnect the charger completely. Total isolation is the only surefire way to eliminate all unanticipated possibilities of things backfeeding into it....because who knows what might get sent back when 24kj discharges across that gap :-o

I plan to do some 5kj shots today to see how it stands up to repetition. Those spark gap knobs are solid brass on the inside. The individual cap strings are sitting at about 7 volts each after a discharge, none of them reversed. The spark gap is built on slots in the base, so I can spread or close the gap by loosening the bolts. I'm able to discharge as low as 1kv.

Full power discharge is getting closer!!!!!

Backyard Skunkworks

Fri Feb 08 2008, 05:10AM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Whoa!

This is totally insane!

This has got to be one of the coolest electrical projects of all time!

I remember reading something somewhere about being able to get water to explode very violently when discharging this kind of energy through it, maybe that would be another experiment?

EDIT:
A quick googling turned up the page, http://www.eskimo.com/~billb/amateur/capexpt.html. That guy had a 33.75kJ bank @150kV and did a few crazy things including coin shrinkage, exploding water and other items, etc.

Andyman

Fri Feb 08 2008, 06:33AM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

Cool! I hopefully will try to use a triggered gap on my 800v bank. It's going to be tough though, the gap will have to be only a few thousandths of an inch. But that will be easier with a feeler gauge.
It would be interesting to try and contain the exploding water and use it to accelerate a projectile...

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